If you are into rooting, installing custom recoveries like TWRP/CWM, and flashing custom ROMs, then whether or not you know it or not, you must, must make a backup of EFS partition of your OnePlus One. And keep it safe, always! An EFS partition backup could prove to be a big lifesaver if you ever run into trouble, when your OnePlus One gets bricked while flashing a custom ROM, or applying some memory leak fix.

Without any doubt, it’s best to create and save a EFS partition backup on your PC, so that in times on need, you can un-brick your OnePlus One easily using the EFS partition. When you lose your IMEI, you can use EFS partition to get the restore IMEI on your OnePlus One back.

Go to Settings > About phone, and then tap ‘Build number’ 7 times to unlock developer options.

Go back to Settings, then choose now visible ‘Developer options’. Find the ‘USB debugging’ option and use its toggle button to enable it. Accept warning by tapping on OK button.

Connect your OnePlus One to PC now. You will get a pop-up as shown below on your phone when you connect for the first time after enabling USB debugging. Select ‘Always allow..’ checkbox and then tap on OK button.